Continued discussion from https://groups.google.com/d/topic/haskell-cafe/-e-xaCEbd-w/discussion https://groups.google.com/d/topic/haskell-cafe/kM_-NvXAcx8/discussion Thank you for all the answeres and thinkings; Here's zipWithN for general Zip functors: [1] . This, together with [2] may constitute a small hackage. A modification from Wren's idea to [1] is the use of fmap instead of repeat. I'm wondering if there are any laws for Zip functors. I first thought that there are similarity between Zips and Applicatives, as [3] states
instance Applicative f => Zip f where zip = liftA2 (,)
However, my intuition is that zipping two arrays should result in an array of size of the same order as two, giving rise to a Zip functor law candidate: zipWith const xs $ zipWith const xs ys == zipWith const xs ys which is violated by the above statement "zip = liftA2 (,)" . [1] https://github.com/nushio3/practice/blob/master/variable-arity/ZipWithN-2.hs [2] https://github.com/nushio3/practice/blob/master/free-objects/zipf-12.hs [3] http://hackage.haskell.org/packages/archive/TypeCompose/0.9.7/doc/html/Data-... -- Takayuki MURANUSHI The Hakubi Center for Advanced Research, Kyoto University http://www.hakubi.kyoto-u.ac.jp/02_mem/h22/muranushi.html